Were those steel BB or lead BB?
I used to run plated lead BB on coyotes before they took those off the table here, and can tell you that TSS does a much better job of terminal ballistics. The only downside is the stuff is stupid expensive.
There is no doubt that the number of pellets in the air using a 10GA can be higher than a 12GA (or 20GA), but in terms of what happens at distance... the velocity and density determines the outcome in terms of penetration of the TSS pellet. Tungsten also patterns very well due to the pellets not loosing shape.
We used these Hornady nickel plated BB heavy magnums but found that their practical range was roughly 50 to 65 yards, not 100 unless you got a golden BB to hit the lottery. Stinging a coyote at that distance is one thing, but smashing the off button is another.
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The basic difference in the density and hardness of tungsten versus lead or steel becomes the story and the results basically favor the high density projectile being able to get to those distances with enough velocity to penetrate hide/flesh/bones.
There are some free-ware shotgun ballistics calculators floating around on the web, and if you play with the steel versus lead versus tungsten, unless you count the $$ the tungsten always wins.